In an image processing apparatus, a binary image generating unit generates a binary image from a multi-value image, a ruled line candidate extracting unit extracts ruled line candidate pixels constituting a ruled line from the binary image, an edge detecting unit determines, from the multi-value image, target pixels that are positioned near the ruled line candidate pixels and detects edge information indicative of whether each target pixel constitutes an edge, and a ruled line obtaining unit obtains a ruled line from the multi-value image based on the edge information detected by the edge detecting unit.